Image forming apparatuses such as electrophotography apparatuses and electrostatic recording apparatuses form an image by developing an electrostatic latent image formed on a photoconductor with a toner, transferring the formed toner image onto a recording medium such as a sheet, and after this, fixing the transferred image by heating. In the formation of a full-color image, four colors of toners of black, yellow, magenta, and cyan are used for development. After toner images of the respective colors are transferred onto a recording medium and overlaid together, the images are simultaneously fixed by heating.
In order to reduce environmental impacts to the earth, considerations are being given to reducing the fixing temperature of the toner. However, a toner having a low melting point has poor heat resistant storage stability. Therefore, it is requested to satisfy low temperature fixability and heat resistant storage stability simultaneously. For example, PTL 1 describes an attempt to simultaneously satisfy low temperature fixability and heat resistant storage stability by optimizing the amount of crystalline polyester to be incorporated into the toner according to the particle size distribution of the toner. PTL 2 describes an attempt to simultaneously satisfy low temperature fixability and heat resistant storage stability, and to secure a separating property, by realizing compatible state and incompatible state of crystalline polyester in the toner simultaneously.